Signatures of a Pressure-Induced Topological Quantum Phase Transition in BiTeI

We report the observation of two signatures of a pressure-induced topological quantum phase transition in the polar semiconductor BiTeI using x-ray powder diffraction and infrared spectroscopy. The x-ray data confirm that BiTeI remains in its ambient-pressure structure up to 8 GPa. The lattice parameter ratio c/a shows a minimum between 2.0-2.9 GPa, indicating an enhanced c-axis bonding through pz band crossing as expected during the transition. Over the same pressure range, the infrared spectra reveal a maximum in the optical spectral weight of the charge carriers, reflecting the closing and reopening of the semiconducting band gap. Both of these features are characteristics of a topological quantum phase transition, and are consistent with a recent theoretical proposal.Comment: revised final versio

Research on human placenta-derived mesenchymal stem cells transfected with pIRES2-EGFP-VEGF165 using liposome

The experiment adopting reverse transcription polymerase chain reaction (RT-PCR) technology, amplified hVEGF165 gene fragments from human leukemia cells HL-60. hVEGF165 gene was reconstructed in pIRES2-EGFP and transferred into the human placenta-derived mesenchymal stem cells (HPMSCs) by liposome-mediated method successfully. The mRNA and protein of hVEGF165 in the transferred cells was detected by RT-PCR and Western blot, and the results showed that hVEGF165mRNA and the protein expressed by HPMSCs transfected with pIRES2-EGFP-hVEGF165 was significantly more than HPMSCs transfected with pIRES2-EGFP. EGFP expression was observed under fluorescence microscope, which proved that the report gene was successfully transferred to the target cells. hVEGF biology activity and cell proliferation activity of HPMSCS transfected with pIRES2-EGFPhVEGF165 was detected by MTT array, which showed that hVEGF165 can promote the proliferation of HPMSCS; however, hVEGF165 biology activity of HPMSCS transfected with pIRES2-EGFP-hVEGF165 was significantly more than HPMSCs transfected with pIRES2-EGFP.  Identification of multipotentiality showed that HPMSCS transfected with pIRES2-EGFP-VEGF165 still maintained multipotentiality.Key words: Transfect, human placenta-derived mesenchymal stem cells, hVEGF165

Density Matrix Approach to Local Hilbert Space Reduction

We present a density matrix approach for treating systems with a large or infinite number of degrees of freedom per site with exact diagonalization or the density matrix renormalization group. The method is demonstrated on the 1D Holstein model of electrons coupled to Einstein phonons. In this system, two or three optimized phonon modes per site give results as accurate as with 10-100 bare phonon levels per site.Comment: 4 pages, 4 figure

Magnetic Inversion Symmetry Breaking and Ferroelectricity in TbMnO\u3csub\u3e3\u3c/sub\u3e

TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature TN\u3c41  K is accompanied by ferroelectric order for T\u3c28  K. To understand this, we establish the magnetic structure above and below the ferroelectric transition using neutron diffraction. In the paraelectric phase, the spin structure is incommensurate and longitudinally modulated. In the ferroelectric phase, however, there is a transverse incommensurate spiral. We show that the spiral breaks spatial inversion symmetry and can account for magnetoelectricity in TbMnO3

Theory of Spin Injection in Two-dimensional Metals with Proximity-Induced Spin-Orbit Coupling

Spin injection is a powerful experimental probe into a wealth of nonequilibrium spin-dependent phenomena displayed by materials with spin-orbit coupling (SOC). Here, we develop a theory of coupled spin-charge diffusive transport in two-dimensional spin-valve devices. The theory describes a realistic proximity-induced SOC with both spatially uniform and random components of the SOC due to adatoms and imperfections, and applies to the two dimensional electron gases found in two-dimensional materials and van der Walls heterostructures. The various charge-to-spin conversion mechanisms known to be present in diffusive metals, including the spin Hall effect and several mechanisms contributing current-induced spin polarization are accounted for. Our analysis shows that the dominant conversion mechanisms can be discerned by analyzing the nonlocal resistance of the spin-valve for different polarizations of the injected spins and as a function of the applied in-plane magnetic field

Pressure-Induced Magnetic Crossover Driven by Hydrogen Bonding in CuF2(H2O)2(3-chloropyridine)

Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with an enhanced ab-plane hydrogen bonding network yields a three dimensional superexchange web between copper centers that triggers a reversible magnetic crossover. Similar pressure- and strain-driven crossover mechanisms involving coordinated motion of hydrogen bond networks may play out in other quantum magnets

Numerical study of the E⊗eE\otimes e Jahn-Teller polaron and bipolaron

The properties of the polaron and bipolaron are explored in the 1D Jahn-Teller model with dynamical quantum phonons. The ground-state properties of the polaron and bipolaron are computed using a recently developed variational method. Dynamical properties of the ground state of a polaron are investigated by calculating the optical conductivity $\sigma(\omega)$. Our numerical results suggest that the Jahn-Teller and Holstein polarons are similar. However, in the strong-coupling regime qualitative differences in $\sigma(\omega)$ between the two models are found and discussed. The influence of the electron-phonon coupling and the electrostatic repulsion on the bipolaron binding energy, bipolaron masses, and correlation functions is investigated.Comment: 9 pages including 11 figures. To appear in PR

Functional significance of the hepaCAM gene in bladder cancer

<p>Abstract</p> <p>Background</p> <p>The hepaCAM gene encodes a new immunoglobulin-like cell adhesion molecule, and its expression is suppressed in a variety of human cancers. Additionally, hepaCAM possesses properties often observed in tumor suppressor genes. However, the expression and biological function of hepaCAM has not been investigated in bladder cancer. Therefore we sought to examine hepaCAM expression and the relationship between its structure and function in human transitional cell carcinoma of bladder (TCCB).</p> <p>Materials and methods</p> <p>HepaCAM expression was evaluated in 28 normal and 34 TCCB bladder specimens and 2 TCCB cell lines using semi-quantitative RT-PCR. The wild-type hepaCAM and the extracellular domain-truncated mutant gene were transfected into the TCCB cell line T24, and the biological properties of both the wild-type gene and the domain-truncated mutant were then assessed.</p> <p>Results</p> <p>HepaCAM expression was down-regulated in 82% (28/34) of TCCB specimens and undetectable in the 2 TCCB cell lines tested. The localization of hepaCAM appeared to be dependent on cell density in T24 cells. In widely spread cells, hepaCAM accumulated on the perinuclear membrane and the cell surface protrusions, whereas in confluent cells, hepaCAM was predominantly localized at the sites of cell-cell contacts on the cell membrane. Functionally, hepaCAM expressed not only increased cell spreading, delayed cell detachment, enhanced wound healing and increased cell invasion; it also inhibited cell growth (P < 0.01). When the extracellular domain was deleted, the localization of hepaCAM was significantly altered, and it lost both its adhesive function and its influence on cell growth.</p> <p>Conclusions</p> <p>HepaCAM is involved in cell adhesion and growth control, and its expression is frequently silenced in TCCB. The extracellular domain of hepaCAM is essential to its physiological and biological functions.</p

Prenatal allergen and diesel exhaust exposure and their effects on allergy in adult offspring mice

Multiple studies have suggested that prenatal exposure to either allergens or air pollution may increase the risk for the development of allergic immune responses in young offspring. However, the effects of prenatal environmental exposures on adult offspring have not been well-studied. We hypothesized that combined prenatal exposure to Aspergillus fumigatus (A. fumigatus) allergen and diesel exhaust particles will be associated with altered IgE production, airway inflammation, airway hyperreactivity (AHR), and airway remodeling of adult offspring. Following sensitization via the airway route to A. fumigatus and mating, pregnant BALB/c mice were exposed to additional A. fumigatus and/or diesel exhaust particles. At age 9-10 weeks, their offspring were sensitized and challenged with A. fumigatus. We found that adult offspring from mice that were exposed to A. fumigatus or diesel exhaust particles during pregnancy experienced decreases in IgE production. Adult offspring of mice that were exposed to both A. fumigatus and diesel exhaust particles during pregnancy experienced decreases in airway eosinophilia. These results suggest that, in this model, allergen and/or diesel administration during pregnancy may be associated with protection from developing systemic and airway allergic immune responses in the adult offspring